Negative electrode material for a rechargeable battery and method for producing the same
The invention relates to An active material for a rechargeable lithium ion battery, comprising metal (M) based particles and a silicon oxide SiO x with 0<x<2, wherein said SiO x is an intimate mixture of amorphous silicon (Si) and crystalline silicon dioxide (SiO 2 ); wherein the metal (M) is preferably selected from the group consisting of Si, Sn, In, Al, Fe and combinations thereof.
1. A compound comprising an active material for a rechargeable lithium-ion battery and a lithium ion-conductive carbon-based material, whereby the active material comprises Si-based particles and a silicon oxide SiO x with 0<x<2, wherein said SiO x is an intimate mixture of amorphous silicon (Si) and crystalline silicon dioxide (SiO 2 ), whereby said compound is characterized by a ratio of the weight of the carbon versus the sum of the weights of Si-based particles and the SiO x , expressed as (Si+SiO x ):C, of between 33:1 and 1:1.
2. The compound according to claim 1 , whereby the ratio of the weight of the carbon versus the sum of the weights of Si-based particles and the SiO x , expressed as (Si+SiO x ):C, is between 9:1 and 1.5:1.
3. The compound according to claim 1 , wherein the Si-based particles have an average diameter of at least 10 nm and of at most 200 nm.
4. The compound according to claim 1 , wherein the SiO x contains domains comprising metallic Si, said domains having a dimension of between 1 nm and 5 nm.
5. The compound according to claim 1 , wherein said SiO x is in the form of SiO x particles.
6. The compound according to claim 1 , wherein said SiO x is in the form of a layer at least partially covering said Si-based particles.
7. The compound according to claim 6 , wherein the SiO x layer has a thickness of at least 1.0 nm and at most 20 nm.
8. The compound according to claim 6 , characterized by a ratio expressed as the average diameter of the metal particles: the thickness of the SiO x layer of at least 1:1 and at most 200:1.
9. The compound according to claim 1 , wherein said SiO x is in the form of a matrix.
10. The compound according to claim 1 , wherein the Si is chosen from the group consisting of (i) pure crystalline silicon; (ii) a homogeneous mixture of silicon- and metal-oxides, having the formula SiO x (M′ a O b ) y , with 0<x<1 and 0≦y<1, wherein a and b are selected to provide electroneutrality, and wherein M′ is one or more of Ca, Mg, Li, Al, and Zr; (iii) an alloy of Si; and (iv) the silicon of any one of (i) to (iii) having an amorphous SiO z surface layer, with 0<z<2, said surface layer having an average thickness of between 0.5 nm and 10 nm.
11. The compound according to claim 1 , wherein 0.3≦x≦1.5.
12. A process for preparing the active material of the compound of claim 1 , comprising:
a. providing a solution comprising an anti-agglomeration agent; a silicon comprising organic compound and a suitable solvent;
b. heating up said solution to form a suspension of SiO 2 and Si in said suitable solvent;
c. adding Si-based particles to said suspension; and
d. firing said suspension to a temperature between 500 and 1300° C. in a non-oxidizing atmosphere.
13. The process of claim 12 , wherein the silicon containing organic compound is an alkyl ester of orthosilicic acid.